Center for Operational Products and Services (CO-OPS)

Modernizing Water Level Vertical Control through cGNSSGNSS for Vertical Control at NOAA’s National Water Level Observation Network (NWLON) StationUSCG Civil GPS Service Interface Committee MeetingSeptember 24-25, 2018Adria Schneck, CO-OPS

Center for Operational Products and Services (CO-OPS)

National Water Level Observation Network (NWLON)

A network of 210 continuously operating water level stations throughout the United States.

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Center for Operational Products and Services (CO-OPS)

Vertical ControlOf

Sensor & Datum

Over a 19-year NTDE:

Vertical movement of the water level sensor relative to

the local Station Datum must be <1.2 cm

Vertical position of the Station Datum relative to

geodetic control must be <0.9 cm

Center for Operational Products and Services (CO-OPS)

Bench Mark NetworkPrimary Means of Vertical Control

Galveston, TXBerwick, Atchafalaya River, LA

Center for Operational Products and Services (CO-OPS)

Vertical ControlToday

● Establish station datum

● Tidal bench mark network installation

● Periodic leveling surveys to tidal bench mark network in accordance

with Federal Geodetic Data Committee (FGDC) standards to measure

sensor elevation relative to land

● Connection to National Spatial Reference System (NSRS) wherever

possible○ Differential surveying ○ Campaign GPS observation ties

■ Each station has one GPS bench mark■ One 4 hour observation every five years (annual w/ high RSL trends)

Initial incorporation of GNSS

Center for Operational Products and Services (CO-OPS)

Land Motion Stations with

NWLON/CORS Collocation

“All GLOSS sites must be equipped with Continuous GNSS antennas

located as close to the gauge as possible, or connected to the gauge

with a regularly maintained geodetic tie. CGNSS records support

studies of vertical land movement and satellite altimeter calibration.”

UNESCO\IOC Manual on Sea Level Measurement and Interpretation, Vol V (2016)

Crescent City, CA

CO-OPS Strategic Vision for GNSS-Based Vertical

Control

Leading the world in Earth system observationGlobal leader in water level observations

Team

CO-OPS GNSS Working Group ● Developed Strategic

Vision● Held NOAA cGNSS

Workshop with National Geodetic Survey (NGS), Office of Coast Survey and Office of Climate

● Developed draft implementation plan

● Is expanding it NGS membership

● Guiding path forward

Berry Books

Wendy Writer

Eric Breur

Chung-Chu Teng

Greg Dusek

Nic Kinsman (NGS)

Manoj SamantEric Breuer Peter Stone

Manoj SamantLaura Rear-McLaughlin

John Stepnoski

Mark Bailey

Jerry Hovis

Louis Licate

Greg Dusek

George Story

Center for Operational Products and Services (CO-OPS)

Priority 1: Sensor Vertical Position

Monitoring & accounting for vertical movement of water level sensorsGoal 1.1: Implement GNSS as a means of measuring sensor stability for various timescales and in a range of environments. Goal 1.2: Realize station datum by referencing the ellipsoid using GNSS. Goal 1.3: Reduce check leveling at stations wherever possible.

Center for Operational Products and Services (CO-OPS)

Priority 2: Reference Framework Connection

Linking water level stations to national & global reference systemsGoal 2.1: Improve GNSS-based connections between water level datums and NSRS at all stations. Goal 2.2: Increase spatial and temporal VDatum coverage and reduce VDatum transformation errors. Goal 2.3: Increase stakeholder access to water level datums through improved connectivity across existing and new databases.

Center for Operational Products and Services (CO-OPS)

Priority 3: Vertical Land Motion Component of Relative Sea Level Trends

Understanding the movement of land near water level stationsGoal 3.1: Support determination of the land and ocean components of relative sea level change at long-term NWLON stations using GNSS. Goal 3.2: Investigate the resolution of regional and local variability in absolute sea level change. Goal 3.3: Enhance utility of CO-OPS’ suite of sea level products for stakeholders.

Center for Operational Products and Services (CO-OPS)

What’s Next?

01

Continue Installations

Continue working with Global Sea Level System (GLOSS) to co-locate cGNSS sensors at NWLON stations.

02

Collaborate with NGS

Strengthen partnership with NGS to align strategies and detail joint initiatives to move vision forward.

03

Detail Implementation Plan

With close consultation with NGS, CO-OPS seeks to complete a detailed five-year implementation plan by the end of 2018.

Center for Operational Products and Services (CO-OPS)

Vertical ControlFuture?

● Continuous monitoring of NWLON configuration stability

● Connections to the National Spatial Reference System (NSRS)

everywhere: ○ Connections via cGNSS, where possible ○ Connections via static/campaign GNSS will be more comprehensive,

systematic, & utilize longer occupations

● Targeted prioritization of geodetic leveling surveys

● Solutions for vertical control in offshore or unstable areas

● Increased participation in international collaboration on observing

global sea level trends

Center for Operational Products and Services (CO-OPS)

Thank You